Method of fitting pistons to engime-cylinders.



w. rvlcbonmAcK m. s. SEARLEJ METHOD OF FITTING PISTONS T0 ENGINE CYLINDERS. APPLICATION FILED JUNE 7. I915- Patented Apr. 25,1916.

WIT/V588 l/IH/E/I/TORS Arron/m5 MACK and GEORGE S. SEARLE, residing at Rochester, in the county of Monroe and f. it.

LIAM MGCORMACK AND GEORGES. SEARLE, OF ROCHESTER, NEW YORK. k

Specification o METHOD or FITTING- rIsTons 'ro nncinn-omnnnns.

etters Patent.

Patented Apt. 25, T916.

original application filed March 1a, 1915, Serial No. 14,154. Divided and this application filed June 7,

To all tvhom it may concern Be it known that we, WILLIAM McCon- State of New York, have invented certain new and useful Improvements in Methods of Fitting Pistons to Engine-Cylinders; and we do hereby declare the followingto be a full, clear, and exact description of the same, reference being had to the accompanying drawings, forming a part of this specification, and to the reference-numerals marked thereon.

Our present invention relates to engines and more particularly to internal combustion engines, and it has for its object to provide a simple, cheap and efficient method of fitting pistons and engine cylinders. to each other. with such precision that less reliance need be placed upon the usual piston ring for holding compression and for'preventing fieposits of carbon in the explosion cham- The invention is applicable during the process of manufacture but may be also utilized in fitting new pistons to old cylinders that have become worn in connection I with the pistons originally associated therewith, but in either instance, the contacting or wearing surfaces are, by the practice of the invention, improved in quality beyond that attained by any revious method of which we are aware with the exception of that set forth in our co-pending application, Serial No. 14,154, filed March 13, 1915, of which this is a-division.

To these and other ends the invention resides in certain improvements and combinaall. as Wlll be hereinafter tions of parts, more fully described, the novel features being pointed out in-the claim at the end of the specification.

In the drawings: Figure 1 is a central longitudinal section through an engine cylinder in process of preparation by a method,

embodying our invention; Fig. 2 is a side elevation partly broken away of an apparatus in process of preparing a piston by a method embodying our invention, the piston being partly shown in side elevation; Fig. 3

is a bottom plan view of the apparatus shown in Fig. 1 in partial section on the line 3-3 of Fig. 1; Fig. 4 is a top plan view of the apparatus shown in Fig. 2.

1915. Serial No. 32,571.

Similar reference numerals throughout the several figures indicate the same parts.

In boring engine cylinders and turning plstons therefor, peripherally extending tool marks are sure to be left on both surfaces. While the prominence of these may be reduced by extended wear against each other through the running of the engine under its own power or otherwise, they cannot by these means be entirely removed for the reaand cylinder are rendered far more smooth 7 and frictionless than are those of a well worn engine.

Suitable apparatus for carrying out the invention is shown in the accompanying drawing and referring first to Figs. 1 and 3 thereof, the cylinder 1 is first bored and tool finished to only approximately the required internal diameter, the walls being left a little thicker than-would ordinarily be the case. We insert in this cylinder a master piston '2 having a connecting rod 3 driven by any suitable means. This master piston can be expanded and retracted as it is made in two halves as shown in Fig. 3. Screws 4 connecting the respective halves are used to draw them together while they may be forced apart by set screws 5 and in this way, the maximum diameter of the cylinder can be accurately controlled as will be understood. When first inserted, the master piston 2 is contracted to a substantially less diameter than that of the finished piston that is to be ultimately assembled with the cylinder in order to enter the latter at all and the cylinder is then subjected to prolonged reciprocations of the master piston which should be arranged to rotate as well as reciprocate in order that its grinding action may be uniformly distributed around the walls of the cylinder. suitable abrasive, such as glass powder, is flowed. between the surfaces and the operationis kept up until all signs of tool marks and other irregularities have disappeared and the cylinder has been enlarged to the exact required internal diameter. During this process, the master piston 2 is expanded slightly, from time to time, by means of the screws 4 and 5 as required.

Next referring more particularly to Figs. 2 and 4, the piston 6 that is to mate with the cylinder 1 is treated in an exactly complementary manner in that it is tool finished removed and of the exact size to make a tight fit with the cylinder 1. In order to absolutely insure the even contact and exact parallelism of the piston surface with the cylinder wall'the two are then coupled together and subjected to relative reciprocation, a small amount of abrasive being usually used untilthe freedom of movement required in the operation of the engine is acquired. All irregularitles have now been I removed from both surfaces,,yet the movement may be continued before assembling the engine as long as desired or as can be afforded to giie that further polish that the wear of metal upon metal only can produce.

If by the time the two surfaces have been brought to the degree of perfection indicated (which is to be done regardless of any other considerations) the wear has been such that the fit is even to the slightest extent too loose, weare able to compensate for it by a further treatment, in accordance with the invention described and claimed in our prior pending application, Serial No. 14,154, filed March 13, 1915, of which this application is a division.

e claim as our invention:

The method -of fitting a piston and an engine cylinder to each other which consists in subjecting the tool finished friction surface of one for a prolonged period to the wearing effect of a master grinding element formed in accordance with the other and adjusting the wearing surface of the master element progressively toward the wearing surface of the member as the grinding progresses, the relative movement of the member and the grinding'element being such as to include a longitudinal reciprocatory motion similar to that of the finished piston and cylinder working as an engine couple. Y .WILLIAM MCCORMACK.

GEORGE S. SEARLE.

Witnesses RUssELL B. GRIFFITH, HARRIET T. VAY. 

